The World Anti-Doping Agency had added the substance, also called mildronate, to its banned list on Jan 1 but Sharapova had failed to read the revised advice. She faces paying for the oversight with her career.

Sharapova made the announcement at the Downtown Hotel in LACredit:
AFP

The repercussions are likely to be savage for an athlete who earned $23 million (£16.1 million) last year in endorsements alone. Sharapova will incur up to a four-year ban from tennis if she is found to have taken meldonium intentionally to improve her performance, and two years if the authorities deem it was unintentional. For the wealthiest female athlete on the planet, it represents a staggering fall from grace. Sharapova was the darling of women’s tennis, by a distance its most marketable property. Now, at the age of 28, the young woman who exploded to prominence with her 2004 Wimbledon triumph as a teenager finds herself engulfed in ignominy.

Her provisional ban will start on March 12. John Haggerty, Sharapova’s lawyer, said that she would not fight it by asking for the B sample to be tested. She insisted that her use of the drug was purely medicinal, but the ITF’s rationale for including meldonium on their banned list was unambiguous. “Meldonium was added because of evidence of its use by athletes for the intention of enhancing performance,” the organisation said.

The most chastening moment of Sharapova's career

It was, by any standard, one of the most grimly startling moments tennis had ever known. Ever since Sharapova’s advisers had served notice that she would be making a “major announcement” at noon California time, conjecture had mounted that the five-time major champion would be confirming her intention to retire after playing only three tournaments in the past eight months.

When the ballroom at the LA Hotel Downtown was fitted out with a floor-to-ceiling curtain, murmurs bubbled that Sharapova, ever the corporate creature, was simply about to unveil her latest range of sweets.

But the presence in the room of Sharapovas’ parents, Yuri and Yelena, hinted that something more dramatic was afoot. So did the fact that she slunk to centre stage in a black dress, a far cry from her usual vibrant ensembles. The bleakness of her words were more than a match for her dour choice of fashion. “I have let my fans down, I have let my sport down,” she said, her voice trembling. “I face consequences.”

Cynics thought the press conference would be just another product endorsement

The International Tennis Federation disclosed that the positive test took place on the day of Sharapova’s last match, a quarter-final defeat by Serena Williams at the Australian Open. Sharapova explained that she had taken the drug for a combination of reasons, including a magnesium deficiency, an irregular electrocardiogram result, and a family history of diabetes. “It made me healthy – that’s why I continued to take it.”

In what was comfortably the most chastening two-minute address of her life, Sharapova said: “A few days ago I received a letter from the ITF, saying that I had failed a drug test at the Australian Open. I take full responsibility. I have made a huge mistake.”

Sharapova disclosed that she had been taken the drug, whose trade name is Meldronit, for the past 10 years, after receiving a prescription from her family doctor. She claimed that she was unaware that it was also known as meldonium until she read the correspondence from the ITF about her failed test in Melbourne.

Has tennis seen the last of Sharapova?

The reaction from the Women’s Tennis Federation was swift and sombre. Steve Simon, the WTA chief executive, said: “I am very saddened to hear this news about Maria. She is a leader and I have always known her to be a woman of great integrity. Nevertheless, as Maria acknowledged, it is all players’ responsibility to know what they put in their body and if it is permissible. The matter is now in the hands of the Tennis Anti-Doping Programme. The WTA will support the decisions reached through this process.”

Tennis has had to confront doping scandals before, but nothing on this scale. Greg Rusedski tested positive for nandrolone in 2003 but was subsequently cleared of any wrongdoing. Mariano Puerta, runner-up at the 2005 French Open, was banned for eight years after taking the stimulant etilefrine. If Sharapova is seeking any solace at so dispiriting a juncture, she might reflect upon the more recent case of Marin Cilic. The Croatian was given a nine-month ban for a failed test but rebounded to win the 2014 US Open.

Whether Sharapova is capable of such a return is a moot point. Her body has failed her at frequent points of late, especially her deteriorating shoulder. But she left no doubt about her resolve to write another act. “I don’t want to end my career this way,” she said, tearfully. “I really hope I will be given another chance to play this game.”

Even in the midst of her greatest torment, Sharapova, remarkably, even struck a seam of the blackest humour. Poking fun at the rumours of retirement that preceded this impromptu carpet, the world No 7 said: “If I was ever going to make an announcement about that, it would not be at a downtown Los Angeles hotel with this rather ugly carpet.” Ever the fashionista, she had been at Vanity Fair’s post-Oscars party in the city only eight days earlier.